Process for increasing molecular weight of a polymer

ABSTRACT

By conducting solution polymerization in the presence of minor amounts of water, higher molecular weight polymers are obtained.

This invention relates to novel polyacrylic hot melt adhesives and tomethods for preparing same.

Adhesives can be divided into three categories: solvent borne, waterborne and 100% solids. Materials in the first two categories must besubjected to a vehicle removal process, subsequent to coating and/orlaminating operations. In the case of water borne adhesives, thisprocedure is uneconomical in terms of energy and time consumption.Solvent borne adhesives are somewhat more economical in this repectrequiring less time and energy, however, the solvent removal processpresents pollution, fire and explosion hazards. Hot melts areessentially 100% solids adhesives and therefore no vehicle removaloperations are necessary. These materials are applied in a molten stateand are then cooled rapidly with the aid of a chill roll. Therefore,coating or laminating operations can be conducted at higher speeds withless equipment, lower energy consumption and greater safety than withvehicle borne adhesives.

Most hot melt adhesives (particularly pressure sensitive adhesives) areblends of elastomers with plasticizer and tackifier resins derived fromnatural rosins. These adhesives generally exhibit poor clarity and deepcoloration or both which are undesirable in applications wherein theadhesive will be visible (e.g., transparent laminations). Many of theelastomers employed in these adhesives contain unsaturated chemicalbonds (e.g., styrene-butadiene block copolymers), these bonds arevulnerable to attack by oxygen and ultraviolet radiation. Thisvulnerability contributes to loss of adhesive properties anddiscoloration on ageing, particularly in outdoor applications.

The term "hot melts" as employed here is meant to include both pressuresensitive adhesives and laminating adhesives. An excellent compendium ofhot melt adhesives is contained in the book Hot Melt Adhesives, NoyesData Corporation (1974).

The novel polyacrylic hot melt adhesives of the instant inventionrequire no nonacrylic additives, are only very lightly colored and aresubstantially insensitive toward oxidation and ultraviolet exposure.

The polyacrylic hot melt adhesives of the invention are compositionscomprising a blend of:

A. from 5 to about 95 parts by weight of an addition copolymer having aTg in the range of from about 0 to about -85° C. comprising:

1. from about 85 to 99.5 parts by weight of a monomer or monomersselected from alkyl (C₁₋₁₈) or alkoxyalkyl acrylate which may alsocontain minor amounts of alkyl methacrylates, alkoxyalkyl methacrylates,styrene, acrylonitrile, vinyl acetate, vinyl chloride, vinylidenechloride, ethylene, butadiene, isoprene, vinyl ether and the like;

2. from about 0.5 to about 15 parts by weight of an ethylenicallyunsaturated amine, carboxylic acid or sulfonic acid or mixtures thereofwith

B. from about 5 to about 95 parts by weight of an addition copolymerhaving a Tg in the range of from about 20° to about 150° C. andcomprising:

1. from about 85 to about 99.5 parts by weight of a monomer or monomersselected from a monomer of the formula: ##STR1## (C₁₋₅), lowercycloalkyl (C₅₋₆) or isobornyl, or styrene, acrylonitrile, vinylacetate, vinyl chloride, vinylidene chloride, ethylene, butadiene,isoprene, vinyl ether and the like and

2. from about 0.5 to about 15 parts by weight of an ethylenicallyunsaturated carboxylic or sulfonic acid or an amine or mixtures thereof.

Preferred hot melt adhesive compositions of this invention comprise ablend of:

A. from about 35 to about 90 parts by weight of a copolymer having a Tgin the range of from -20° C. to about -65° C. comprising:

1. from about 88 to about 98.5 parts by weight of a lower alkyl acrylate(C₁₋₈) and

2. from about 1.5 to about 12 parts by weight of an ethylenicallyunsaturated acid or amine with

B. from about 10 to about 65 parts by weight of a copolymer having a Tgof 35° C. or more preferably in the range of from about 35° C. to about110° C. comprising:

1. from about 88 to 98.5 parts by weight of the monomer of the formula:##STR2## wherein R is hydrogen or methyl and R² is lower alkyl, lowercycloalkyl or isobornyl and

2. from about 1.5 to about 12 parts by weight of an ethylenicallyunsaturated carboxylic acid or amine.

Pressure sensitive adhesives can best be prepared employing from about15 to about 30 parts by weight of Copolymer B, supra whereas blendscontaining greater than 30 parts by weight of Copolymer B, supra, aresuitable for use as nontacky laminating adhesives, particularly hot-meltadhesives.

Especially preferred are compositions comprising a blend of:

A. from about 60 to about 85 parts by weight of a copolymer comprising:

1. from about 94 to 98 parts by weight of a monomer selected from butylacrylate, 2-ethylhexyl acrylate, methyl acrylate, ethyl acrylate,isobutyl acrylate, isoamyl acrylate or n-propyl acrylate and

2. from about 2 to about 6 parts by weight of dimethylaminoethylacrylate or methacrylate, diethylaminoethyl acrylate or methacrylate ortert-butylaminoethyl methacrylate with

B. from about 15 to about 40 parts by weight of a copolymer comprising:

1. from about 94 to 98 parts by weight of isobutyl methacrylate,isobornyl acrylate, isobornyl methacrylate, methyl methacrylate and thelike and

2. from about 2 to 6 parts by weight of an acid selected frommethacrylic acid, acrylic acid or itaconic acid.

The preferred systems are compatible, as determined by dissolving thesystem in an organic solvent, casting on a film a surface at a thicknessof about 20 mils, curing the film, and examining it for clarity; if thefilm is clear, the polymers are compatible. To determine compatibility a30% solution of the copolymers is prepared in a suitable solvent such astoluene and the like, blended in the desired proportions and spread on aglass plate at a thickness of about 20 mils. The blend is allowed to airdry for one half hour, dried in a 150° C. oven for three hours, allowedto cool and examined visually for clarity. The systems are consideredcompatible if they form a substantially clear film.

The viscosity of the blends at 177° C. (350° F.) at 100% solids isgenerally in the range of from about 1,000 to about 1,000,000 cps withthe preferred blends having viscosities in the range of from about 1,000to about 250,000 cps.

Blending is preferred since we have found that forming a single polymerfrom the same ratios of monomers as in a blend affords a very poor ifnot totally unsuitable hot melt adhesive.

Examples of acrylate monomers which form polymers having low Tgs includethe methyl, ethyl, n-propyl, isopropyl, isobutyl, sec-butyl, n-butyl,n-pentyl, 2-ethylhexyl, methoxyethyl and ethoxyethyl acrylates.

Examples of monomers which form polymers having Tgs of 20° to 150 ° C.include tert-butyl acrylate, cyclohexyl acrylate and methacrylate alsoincluded are the methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl,sec butyl, tert-butyl, isopentyl, cyclohexyl and isobornylmethacrylates.

The ethylenically unsaturated containing carboxylic acid, sulfonic acidor amine employed in the preparation of the copolymers are monomers havethe following formula: ##STR3## wherein R² is hydrogen, methyl orcarboxy and X is mono- or di-lower alkylamino lower alkoxy carbonyl suchas dimethylaminoethoxycarbonyl, diethylaminoethoxycarbonyl,tert-butylaminoethyoxycarbonyl and the like, sulfo lower alkoxycarbonylsuch as 2-sulfoethoxycarbonyl and the like, a 5- or 6-memberedheterocyclic amine radical such as 2- or 4-pyridyl, 2-quinolyl and thelike, carboxy, lower alkoxy carbonylmethyl, such asmethoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl,butoxycarbonylmethyl and the like or carboxy lower alkyl such ascarboxymethyl and the like. While in general either an acid or amine ora mixture thereof will afford adhesives, it is preferred that thecopolymers with the high Tgs contain the acid and the copolymers withlow Tgs contain the amine.

Examples of the carboxylic acids, sulfonic acids or amines which can beemployed include acrylic acid methacrylic acid, itaconic acid and itsalkyl half-esters such as the methyl, ethyl, propyl, n-butyl esters andthe like 2-sulfoethyl methacrylate, tert-butylaminoethyl methacrylate,dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,dimethylaminoethyl acrylate, diethylaminoethyl acrylate, 2- or4-pyridine, 2-vinylquinoline and the like.

For the purpose of this invention, solution polymerization andespecially sequential solution polymerization is used because of thesuperior adhesive properties of the resulting polymer.

It has been found that by conducting solution polymerizations at refluxtemperatures in the presence of water, higher molecular weight polymersare obtained. The addition of water to the reaction mixture lowers thereflux temperature of the reaction mixture; slows the rate ofdecomposition in the initiator employed in the polymerization andbecause the reaction is conducted at reflux, the oxygen of the air isexcluded from the reaction.

The amount of water employed is dependent upon the initiator, solvent,type of monomers employed and concentration of monomers. In general,water is employed in the range of from about 0.1 parts per 100 parts oftotal monomer employed to about 5.0 parts and, preferably, in the rangeof from 0.1 to 1.0 parts.

The most preferred procedure is not to add the water in one portion butto add water initially in the range of from about 0.1 to about 0.30parts with subsequent multiple additions of water in the range of about0.01 to about 0.12 parts whenever the reflux temperature begins toexceed the desired reaction temperature.

Solvents which can be employed in these solution polymerizations are, ingeneral, organic solvents which when containing water reflux at a lowertemperature than when they are anhydrous. Examples of solvents which canbe employed include aromatic hydrocarbons, such as benzene, toluene,xylene, mesitylene and the like; aliphatic hydrocarbons, such as butane,pentane, hexane, heptane, isooctane and the like, ketones, such asmethylethyl ketone, methylisobutyl ketone and the like; esters, such asethyl acetate, propyl acetate, butyl acetate, ethyl propionate and thelike; ethers, such as butyl ether, anisole and butoxyethanol; alcohols,such as butanol, pentanol and the like; halogenated aliphatichydrocarbons such as chloroform and the like and mixtures of same.

The preferred procedure is to conduct the polymerization in the solventtoluene at a temperature in the range of from about 112° to about 118°C.

In the preparation of the blends it has been found that in sequentialsolution polymerizations water can be added to any or all of thecopolymerizations. For example, in the preparation of hot meltadhesives, either Copolymer A or Copolymer B can be formed first andthat the addition of water at either or both polymerization stepsinvolved causes an increase to the molecular weight of the copolymer. Itis preferred, however, to add water to the second monomer mix to formhigher molecular weight Copolymer A (Tg = -85° to 0° C.

As polymerization catalyst there may be used one or more peroxides whichare known to act as free radical catalysts and which have solubility inaqueous solutions of the emulsifier. Highly convenient are thepersulfates, including ammonium, sodium and potassium persulfates orhydrogen peroxide or the perborates or percarbonates. Preferred are theorganic peroxides used in solution polymerizations including benzoylperoxide, tert-butyl hydroperoxide, cumene peroxide, tetralin peroxide,acetyl peroxide, caproyl peroxide, tert-butyl peracetate, tert-butylperbenzoate, tert-butyl diperpthalate, tert-butyl peroctoate,methylethyl ketone peroxide, tert-butyl perpivalate and the like.

The usual range of catalyst employed is from about 0.01% to about 3% ofcatalyst with reference to the weight of the monomer mixture. Thepreferred range is from about 0.02 to about 1.0% with the range of fromabout 0.05 to about 0.8% being most preferred. The optimum amount ofcatalyst is determined in large part by the nature of the particularmonomers employed including impurities which accompany particularmonomers.

These systems, though normally employed as 100% solids, can, if needed,also be applied by dissolving in a suitable solvent including toluene,xylene, acetone, methylethyl ketone, methylisobutyl ketone, halogenatedhydrocarbons such as chloroform, dichloroethane and the like. While, ingeneral, no additives are needed, the following may be employed:

adhesive agents, such as colophonium, phenol resins, natural resin,conresin, coumarone-indene resin, resinester and hydrated resinderivatives may be incorporated;

fillers and pigments may be added to obtain needed properties. Typicalfillers include: powdered quartz, pearl white barium sulfate, light spar(gypsum), chalk and the like and

antioxidants, ultraviolet inhibitors, plasticizers and pigments may alsobe employed.

PREPARATION OF POLYMERS HAVING Tg's OF 0° C. AND LESS Example 1 --Copolymer of Butyl acrylate and Methacrylic Acid

A monomer mix is prepared from butyl acrylate (98 parts), methacrylicacid (2 parts), tert-butyl peroctoate (0.1 parts) and hydroxyethylmercaptan (0.05 parts). To a flask containing toluene (19.3 parts) isadded 15 parts of the monomer mix and the contents heated to 110° C.with stirring. The remainder of the monomer mix is added at a constantrate over a three hour period at 110° C. The polymerization mixture isheld at 110° C. for 30 minutes and then treated during 30 minutes with asolution prepared from toluene (0.83 parts) and tert-butyl peroctoate(0.2 parts). After the mixture is held at 110° C. for 30 minutes longerand then cooled, there is obtained a solution containing 93.2% by weightof polymer representing a conversion of 100%. The Brookfield Viscosityof the solution at three rpm is 162,000 cps.

By following substantially the procedure of Example 1, the copolymerswith a Tg of 0° or less described in Table I are prepared.

                                      TABLE I                                     __________________________________________________________________________                  EXAMPLE NO                                                      Comonomer - Grams                                                                           2   3   4   5   6   7   8                                       __________________________________________________________________________    Butyl acrylate                                                                              95.7                                                                              96.5                                                                              95  95.7                                                                              75.7                                                                              92  98                                      tert-Butylaminoethyl                                                          methacrylate  4.3 --  --  --  4.3 8   --                                      -Dimethylaminoethyl.5 5   --  --  --  --                                      methacrylate              4.3 --  --  --                                      Acrylic acid                          2                                       2-Ethylhexyl acrylate         20  --  --                                      Total Catalyst (percent by                                                    wt. of monomers)                                                                            0.1 0.2 0.1 0.1 0.1 0.1 0.1                                     2-Hydroxyethyl mercaptan                                                      (percent by wt. of monomer)                                                                     0.1 0.05                                                                              --  --  --  0.05                                    Final Solids (percent by wt.)                                                               81.7                                                                              83.1                                                                              82.3                                                                              81.1                                                                              82.2                                                                              81.4                                                                              71.1.sup.a                              Conversion (%)                                                                              98.4                                                                              100 99.4                                                                              97.7                                                                              99.0                                                                              98.1                                                                              99.8                                    Brookfield Visc. (cps)                                                                      137,000                                                                           189,000                                                                           554,000                                                                           47,500                                                                            57,000                                                                            66,000                                                                            21,100                                  __________________________________________________________________________     .sup.a Diluted with 20 parts toluene                                     

Example 9 -- Copolymer of Butyl acrylate and tert-Butylaminoethylmethacrylate

A solution of toluene (19.3 parts), butyl acrylate (12.4 parts),tert-butylaminoethyl methacrylate (2.58 parts) and 0.10 parts of a 75%solution of tert-butyl perpivalate contained in a flask is heated to 92°C. with stirring for 30 minutes. A monomer mix containing butyl acrylate(70.4 parts), tert-butylaminoethyl methacrylate (14.6 parts) and 0.228parts of a 75% solution of tert-butyl perpivalate is then added at aconstant rate over three hours to the stirred reaction mixture at 92° C.The reaction mixture is maintained at 92° C. for 30 minutes while beingdiluted with toluene (20 parts). A chaser catalyst of toluene (1.25parts) and 0.20 parts of a 75% solution of tert-butyl peripvalate isadded over 30 minutes; the reaction mixture is held at 92° C. for 30minutes following which it is cooled to afford a solution containing67.0% by weight of a polymer representing a conversion of 94.5 % of thetheoretical. The Brookfield viscosity of the solution at six rpm is13,400 cps.

By following substantially the procedure as described in Example 9, thefollowing soft polymers described in Table II are prepared.

                                      TABLE II                                    __________________________________________________________________________                      EXAMPLE NO.                                                 Comonomer - Grams 10  11  12  13  14  15                                      __________________________________________________________________________    Butyl acrylate    90.2                                                                              86.8                                                                              91.6                                                                              88.6                                                                              85  97.5                                    tert-Butylaminoethyl                                                          methacrylate      9.8 13.2                                                                              --  --  --  2.5                                     Dimethylaminoethyl                                                            methacrylate              8.4 11.4                                                                              15  --                                      Final Solids (% by wt.)                                                                         68.4                                                                              68.4                                                                              69.0                                                                              67.7                                                                              73.0.sup.b                                                                        69.1                                    Conversion (%)    97.5                                                                              96.6                                                                              96.2                                                                              95.5                                                                              95.7                                                                              97.4                                    Brookfield Visc. (cps)                                                                          12,600                                                                            13,500                                                                            6,750                                                                             6,200                                                                             17,500                                                                            17,000                                  __________________________________________________________________________                  EXAMPLE NO.                                                     Comonomer - Grams                                                                           16  17  18  19  20  21  22                                      __________________________________________________________________________    Butyl acrylate                                                                              55.7                                                                              75.7                                                                              68  80.7                                                                              48  --  --                                      2-Ethylhexyl acrylate                                                                       40  20  --  --  --  --  --                                      Ethyl acrylate        27.7                                                                              --  --  --  --                                      Methyl acrylate           15  --  --  --                                      Isobutyl acrylate             47.7                                                                              --  --                                      Isoamyl acrylate                  95.7                                                                              --                                      n-Propyl acrylate                     95.7                                    tert-Butylaminoethyl                                                          methacrylate  4.3 4.3 4.3 4.3 4.3 4.3 4.3                                     Final Solids (% by wt.)                                                                     72.7                                                                              72.8                                                                              69.8                                                                              68.2                                                                              75.5                                                                              68.4                                                                              68.2                                    Conversion (%)                                                                              97.8                                                                              98.0                                                                              98.5                                                                              96.2                                                                              96.5                                                                              98.0                                                                              97.7                                    Brookfield Viscosity                                                          (cps)         17,700                                                                            27,150                                                                            29,750                                                                            78,500                                                                            78.500                                                                            11,200                                                                            17,500                                  __________________________________________________________________________     .sup.a Chaser catalyst amounted to 0.4 parts                                  .sup.b Diluted with only 10 parts toluene                                

PREPARATION OF POLYMERS HAVING Tg's OF 20° to 150° C. Example 23 --Isobutyl methacrylate and Methacrylic Acid

A monomer mixture is prepared from isobutyl methacrylate (96.3 parts)and methacrylic acid (3.7 parts). A catalyst solution is prepared fromxylene (11.8 parts) and tert-butyl peroctoate (1.10 parts). To a flaskequipped with a stirrer is added xylene (30.1 parts), 15.1 parts monomermix and 1.4 parts catalyst solution. The contents are heated to 115° C.at which point the remaining monomer solution and 7.96 parts catalystsolution are added at a constant rate over a two hour period with thereaction mixture maintained at 115° C. The remainder of the catalystsolution is added at a uniform rate over 30 minutes. After an additional15 minutes at 115° C., the reaction mixture is cooled and diluted withxylene (72 parts) to afford a solution containing 45.6% by weight ofpolymer representing a conversion of 98.2% of the theoretical. TheBrookfield viscosity of the solution at 30 rpm is 13,440 cps.

By following substantially the procedure of Example 23, the productsdescribed in Table III are prepared.

                                      TABLE III                                   __________________________________________________________________________               EXAMPLE NO.                                                        Comonomer - grams                                                                        24 25 26  27 28 29 30 31 32  33  34                                __________________________________________________________________________    Isobutyl meth-                                                                acrylate      98 94  90 99.5                                                                             98.5                                                                             97            96.9                              tert-Butylaminoethyl                                                          methacrylate                                                                             3.0                3.0                                             Methacrylic acid                                                                            2.0                                                                              6.0 10          2.0                                                                              3.7 5                                     Acrylic acid                                3.1                               2-Sulfoethyl meth-                                                            acrylate                0.5                                                                              1.5                                                Methyl methacrylate              28 27.3                                                                              27                                    Butyl methacrylate                                                                       97 -- --  -- -- -- -- 70 69  68                                    Total catalyst (%                                                             by wt. of monomers)                                                                      1.1                                                                              1.1                                                                              1.1 2.2                                                                              1.1                                                                              1.1                                                                              1.1                                                                              1.1                                                                              1.1 2.2 1.1                               Final Solids (% by                                                            Wt.)       45.0                                                                             45.5                                                                             46.8                                                                              49.5                                                                             45.7                                                                             45.4                                                                             45.2                                                                             45.2                                                                             45.2                                                                              45.1                                                                              45.5                              Conversion (%)                                                                           96.9                                                                             97.9                                                                             100 100                                                                              98.3                                                                             97.6                                                                             97 97.2                                                                             97.3                                                                              97.1                                                                              97.9                              Brookfield Visc.                                                              (cps)         4070                                                                             400,000                                                                           -- 545                                                                              595                                                                              5600                                                                             3160                                                                             18,100                                                                            530,000                                                                           4400                              __________________________________________________________________________                           EXAMPLE NO.                                            Comonomer - grams      35      36      37                                     __________________________________________________________________________    Butyl methacrylate     76.3    --      --                                     Isobornyl methacrylate 20      20      --                                     Isobutyl methacrylate          76.3    76.3                                   Methyl methacrylate                    20                                     Methacrylic acid       3.7     3.7     3.7                                    Total catalyst (% by wt. of monomers)                                                                1.9     1.1     1.9                                    Final Solids (% by wt.)                                                                              44.6    45.0    45.8                                   Conversion (%)         96.3    96.9    98.9                                   Brookfield Viscosity (cps)                                                                           2420    --      7200                                   __________________________________________________________________________

Example 38 -- Isobutyl methacrylate (96.3) -- Itaconic Acid (3.7)

To a flask equipped with a stirrer is added 2-methoxyethanol (12.3parts), toluene (27.4 parts) and itaconic acid (3.7 parts). The contentsare heated to reflux and a monomer mix containing isobutyl methacrylate(96.3 parts), toluene (9.58 parts) and tert-butyl peroctoate (0.93parts) are added at a constant rate over three hours. The reactionmixtures are held at reflux for 15 minutes, treated over a period of onehour with a solution of toluene (5.5 parts) and tert-butyl peroctoate(0.93 parts), diluted with toluene (10.5 parts) and then cooled toafford a polymer solution containing 59.4% by weight of polymerrepresenting a conversion of 98.9% of the theoretical. The Brookfieldviscosity of the solution at 30 rpm is 11,500 cps.

BLENDING OF THE COPOLYMERS TO FORM HOT MELT ADHESIVES

The polymers of Examples 1-23 and the polymers of Examples 23-38 areblended to afford compatible mixtures exhibiting hot melt adhesiveproperties. The blending is accomplished by removing solvent from eachpolymer at 150°-175° C. and 5-10 tor. The required quantities of theindividual polymers are weighed into a beaker, heated to 175° C. andblended to afford the hot melt adhesives of Table IV.

                  TABLE IV                                                        ______________________________________                                                                      Parts by weight                                                               of Polymers of                                                                Examples 23-38                                          Polymers of                                                                              Polymers of                                                                              Per 100 Parts                                   Blend   Example No.                                                                              Example No.                                                                              of Mixture                                      ______________________________________                                        39      23         2          15                                              40      "          2          20                                              41      "          2          25                                              42      "          2          30                                              43      "          2          35                                              44      "          2          40                                              45      "          15         20                                              46      "          15         25                                              47      "          15         30                                              48      "          15         35                                              49      "          5          30                                              50      "          5          35                                              51      "          5          40                                              52      "          6          30                                              53      "          6          35                                              54      "          6          40                                              55      "          7          30                                              56      "          7          40                                              57      "          1          25                                              58      "          1          30                                              59      "          1          35                                              60      "          1          40                                              61      24         1          40                                              62      "          1          50                                              63      "          1          60                                              64      "          1          70                                              65      "          8          35                                              66      25         2          30                                              67      "          2          35                                              68      "          2          40                                              69      "          5          30                                              70      "          5          35                                              71      "          5          40                                              72      "          6          30                                              73      "          6          35                                              74      "          6          40                                              75      "          7          30                                              76      "          7          35                                              77      "          7          40                                              78      26         2          30                                              79      "          2          35                                              80      "          2          40                                              81      "          5          30                                              82      "          5          35                                              83      "          5          40                                              84      "          7          30                                              85      "          7          35                                              86      "          7          40                                              87      27         5          30                                              88      "          5          35                                              89      "          5          40                                              90      "          7          30                                              91      "          7          35                                              92      "          7          40                                              93      28         2          30                                              94      "          2          35                                              95      "          2          40                                              96      "          5          30                                              97      "          5          35                                              98      "          5          40                                              99      "          6          30                                              100     "          6          35                                              101     "          6          40                                              102     "          7          30                                              103     "          7          35                                              104     "          7          40                                              105     29         5          30                                              106     "          5          35                                              107     "          5          40                                              108     "          2          30                                              109     "          2          35                                              110     "          2          40                                              111     "          7          30                                              112     "          7          35                                              113     "          7          40                                              114     30         1          25                                              115     "          1          30                                              116     "          1          35                                              117     "          1          40                                              118     "          2          25                                              119     30         2          30                                              120     "          2          35                                              121     "          2          40                                              122     "          3          10                                              123     "          3          20                                              124     "          4          10                                              125     "          4          20                                              126     "          4          25                                              127     "          4          30                                              128     "          8          35                                              129     31         10         25                                              130     "          10         30                                              131     "          10         35                                              132     "          11         25                                              133     "          11         30                                              134     "          11         35                                              135     "          9          25                                              136     "          9          30                                              137     "          9          35                                              138     "          12         25                                              139     "          12         30                                              140     "          12         35                                              141     "          13         25                                              142     "          13         30                                              143     "          13         35                                              144     "          14         25                                              145     31         14         30                                              146     "          14         35                                              147     32         10         25                                              148     "          10         30                                              149     "          10         35                                              150     "          11         25                                              151     "          11         30                                              152     "          11         35                                              153     "          9          25                                              154     "          9          30                                              155     "          9          35                                              156     "          12         25                                              157     "          12         30                                              158     "          12         35                                              159     "          13         25                                              160     "          13         30                                              161     "          13         35                                              162     "          14         25                                              163     "          14         30                                              164     "          14         35                                              165     33         10         25                                              166     "          10         30                                              167     "          10         35                                              168     "          11         25                                              169     "          11         30                                              170     "          11         35                                              171     "          9          25                                              172     33         9          30                                              173     "          9          35                                              174     "          12         25                                              175     "          12         30                                              176     "          12         35                                              177     "          13         25                                              178     "          13         30                                              179     -          13         35                                              180     "          14         25                                              181     "          14         30                                              182     "          14         35                                              183     34         2          25                                              184     "          2          30                                              185     "          2          35                                              186     "          2          40                                              187     38         2          20                                              188     "          2          25                                              189     "          2          30                                              190     "          2          35                                              191     23         16         20                                              192     "          16         25                                              193     "          16         30                                              194     "          16         35                                              195     "          16         40                                              196     "          17         20                                              197     "          17         25                                              198     "          17         30                                              199     23         17         35                                              200     "          17         40                                              201     "          18         20                                              202     "          18         25                                              203     "          18         30                                              204     "          18         35                                              205     "          18         40                                              206     "          19         20                                              207     "          19         25                                              208     "          19         30                                              209     "          19         35                                              210     "          19         40                                              211     "          20         15                                              212     "          20         20                                              213     "          20         25                                              214     "          20         30                                              215     "          20         35                                              216     "          21         20                                              217     "          21         25                                              218     "          21         30                                              219     "          21         35                                              220     "          21         40                                              221     35         17         20                                              222     "          17         25                                              223     "          17         30                                              224     "          17         35                                              225     "          17         40                                              226     36         17         20                                              227     36         17         25                                              228     "          17         30                                              229     "          17         35                                              230     "          21         15                                              231     "          21         20                                              232     "          21         25                                              233     "          21         30                                              234     "          21         35                                              235     37         18         20                                              236     "          18         25                                              237     "          18         30                                              238     "          18         35                                              239     "          18         40                                              240     "          19         15                                              241     "          19         20                                              242     "          19         25                                              243     "          19         30                                              244     "          19         35                                              245     "          22         15                                              246     "          22         20                                              247     "          22         25                                              248     "          22         30                                              249     "          22         35                                              250     "          20         15                                              251     "          20         20                                              252     "          20         25                                              253     "          20         30                                              254     "          20         35                                              ______________________________________                                    

BLENDING BY SEQUENTIAL SOLUTION POLYMERIZATION

The blends may also be prepared by a sequential solution polymerizationof the monomer composition required for each phase. The low Tg monomersmay be polymerized first, followed by polymerization of the high Tgmonomers, as illustrated by Example I or the high Tg polymers and thenthe low Tg monomers may be polymerized as illustrated by Examples IIthrough XII. The preferred method is the latter. Blends prepared bysequential polymerization of each phase have performance equivalent orsuperior to blends of the separately prepared polymers.

Example I illustrates the sequential polymerization in which the softphase is prepared first followed by the hard phase. The soft phase,butyl acrylate/tert-butylaminoethyl methacrylate = 95.7/4.3, to hardphase, isobutyl methacrylate (IBMA)/methacrylic acid (MAA) = 96.3/3.7,ratio is 72.5/27.5.

EXAMPLE I

A flask containing toluene (5.35 parts), butyl acrylate (10.4 parts),and tert-butylaminoethyl methacrylate (0.47 parts) is heated until thecontents attain 105° C. when tert-butyl peroctoate (0.012 partsdissolved in toluene 0.70 parts) is added. The solution is brought toreflux and held at reflux for forty minutes. A soft phase monomer mixprepared from butylacrylate (59.0 parts), tertbutylaminoethylmethacrylate (2.65 parts), tert-butyl peroctoate (0.031 parts) andtoluene (2.08 parts) is added at a uniform rate over 105 minutes to theflask contents at reflux. Following a 15 minute hold period of chasercatalyst composed of 75% tert-butyl peracetate (0.19 parts) and toluene(0.59 parts) is added over a 45 minute period. The mixture is held atreflux (15 minutes), diluted with toluene (1.24 parts). A hard phasemonomer mix containing isobutyl methacrylate (26.5 parts), methacrylicacid (1.02 parts), toluene (3.58 parts) and 75% tert-butyl peracetate(0.076 parts) is prepared and added at a uniform rate to the reactionmixture over a 50 minute period. Following a 15 minute hold period achaser solution at 75% tert-butyl peracetate (0.37 parts) and toluene(2.1 parts) is added at a uniform rate over 95 minutes. After a 15minute hold period the solution is cooled and it is found to contain83.1% solids (96.6% overall conversion) and to have a viscosity of210,000 cps at 53° C. The polymer blend is stripped of solvent on aflask-evaporator at 175° C. and 5-10 torr.

Example II through VII illustrate the sequential polymerization in whichthe hard phase is prepared first followed by the soft phase.

EXAMPLE II

A hard phase monomer mix is prepared from isobutyl methacrylate (26.5parts), methacrylic acid (1.01 parts), toluene (0.98 parts) andtert-butyl peroctoate (0.45 parts). To a flask containing toluene (7.50parts) is added 19.1% of the monomer mix and the contents are heated toreflux (113° C). Fifteen minutes later the addition of the remainingmonomer mix is started and continued at a constant rate over 40 minuteswhile the flask contents are stirred at reflux. The mixture is held atreflux for 15 minutes and then treated during 30 minutes with theaddition at a uniform rate of a solution prepared from toluene (1.33parts) and tert-butyl peroctoate (0.048 parts). The solution is held atreflux for 15 minutes (122° C.) and then a soft phase monomer mix isprepared from toluene (4.20 parts), butyl acrylate (69.39 parts),tert-butylaminoethyl methacrylate (3.11 parts) and 75% tert-butylperacetate (0.049 parts) is added over 100 minutes at a uniform ratewhile keeping the flask contents at reflux. During the addition, thereaction temperature increases from 122° to 139° C. The reaction mixtureis held at reflux for 15 minutes and then treated by the uniformaddition over 60 minutes of a solution containing toluene (2.84 parts)and 75% tert-butyl peracetate (0.20 parts). After the mixture is held atreflux for 15 minutes longer and then cooled, there is obtained asolution containing 85.5% by weight of polymer representing a conversionof 100%. The product is concentrated on a flash evaporator at 175° C.and 3-5 torr. to a nominally 100% solids, highly viscous liquid.

By following substantially the process of Example II the sequentiallypolymerized hard soft copolymer blends of Examples III through VII areprepared, see Table V. Except for Example VII all of the Examples ofTable V have the same hard and soft phase composition of Example II.

                  TABLE V                                                         ______________________________________                                                 Parts of Hard          Viscosity                                              Polymer per            at 100%                                                100 Parts of           solids and                                    Example No.                                                                            Total Monomer                                                                             Conversion (%)                                                                           177° C. (cps.)                         ______________________________________                                        III      20          100        4200                                          IV       25          99.7       6900                                          V        22.5        100        4000                                          VI       38.4        --         --                                            VII      20.sup.1    99.8       5100                                          ______________________________________                                         .sup.1 Hard phase composition: IBMA/MAA = 94.8/5.2                       

Example VIII illustrates the sequential polymerization in which the hardphase is prepared first followed by the soft phase; however, during thepolymerization of the soft phase, water is added to reduce the reactiontemperature with the result that a higher molecular weight soft phase isformed.

EXAMPLE VIII

A hard phase monomer mix is prepared from isobutyl methacrylte (19.26parts), methacrylic acid (0.74 parts), toluene (0.72 parts), andtert-butyl peroctoate (0.16 parts). To a flask containing toluene (8.18parts) is added 28.7% of the monomer mix and the contents are heated toreflux (115° C.). Fifteen minutes later the addition of the remainingmonomer mix is started and continued at a uniform rate over 40 minuteswhile the flask contents are stirred at reflux. The mixture is held atreflux for 15 minutes and then treated during 30 minutes with theaddition at a constant rate of a solution prepared from toluene (1.34parts) and tert-butyl peroctoate (0.034 parts). The solution is held atreflux for 15 minutes (120° C.) then treated with water (0.24 parts)which reduced the reflux temperature to 107° C. A soft phase monomer mixcontaining butyl acrylate (76.56 parts), tertbutylaminoethylmethacrylate (3.44 parts), 75% tert-butyl peracetate (0.054 parts) andtoluene (3.52 parts) is fed at a constant rate over the next 100minutes. During the addition, the reaction temperature increases from107° to 129° C. The reaction mixture is held at reflux for 15 minutesand then treated with a solution of 75% tert-butyl peracetate (0.054parts) and toluene (2.84 parts) which is added at a uniform rate over 60minutes. The mixture is held for 15 minutes at reflux, diluted withtoluene (23.9 parts) and the water removed as a toluene azeotrope.Toluene (40.85 parts) is used to dilute the polymer which is present asa 55.3% solution (100% conversion) with a Brookfield Visocosity of33,000 cps. The product is concentrated with a flask evaporator at 175°C. and 3-5 torr is a nominally 100% solids, highly viscous liquid with aviscosity of 13.200 cps (Brookfield NBT Viscometer, spindle 27, 20 rpmat 177° C.).

Examples IX through XIX of Table VI are prepared by substantially theprocess of Example VIII. With the exception of Example XIX, thecomposition of the hard and soft phases is as in Example VIII. TheExamples differ in the amount of hard phase and/or the molecular weightof the hard of soft phase. The molecular weight of the hard phase isaltered by changing the initiator level; the molecular weight of thesoft phase is controlled by adjusting the polymerization temperaturewith added water: (1) with no water (Condition A) the polymerizationtemperature ranged from 117°-139° C.; (2) with 0.24 parts of water per100 parts total monomer added prior to the start of the soft phasemonomer addition (Condition B) the polymerization temperature rangedfrom 105°-130° C.; (3) with water added as in Condition B and thenwhenever the polymerization temperature rises to 115° C., 0.08 parts ofwater are added (Condition C).

                                      TABLE VI                                    __________________________________________________________________________         Parts of                                                                      High Tg Percent of Hard         Viscosity                                                                          Viscosity at                             Polymer per                                                                           Phase Initiator                                                                       Soft Phase  Final                                                                             (cps) at                                                                           100% solids                         Example                                                                            100 Parts of                                                                          based on hard                                                                         Water Conversion                                                                          Solids                                                                            Final                                                                              and 177° C.                  No.  Total Polymer                                                                         phase wt.)                                                                            Condition.sup.1                                                                     (%)   (%) Solids                                                                             (cps)                               __________________________________________________________________________    IX   20      0.8     B     99.7  60.2                                                                              81,800                                                                             17,300                              X    20      0.8     C     99.9  55.2                                                                              131,000                                                                            48,000                              XI   20      1.2     C     100   55.3                                                                              93,600                                                                             43,000                              XII  20      0.4     A     98.5  54.2                                                                              21,800                                                                              7,000                              XIII 20      0.4     B     100   55.2                                                                              60,500                                                                             22,000                              XIV  20      0.8     A     100   55.0                                                                              13,100                                                                              5,200                              XV   18      0.8     C     100   55.5                                                                              147,000                                                                             40,700.sup.3                       XVI  18      0.4     B     100   55.5                                                                              47,000                                                                             22,800                              XVII 18      0.4     A     100   55.2                                                                              21,300                                                                              7,600                              XVIII                                                                              15      0.8     C     99.8  55.3                                                                              --   44,200                              XIX.sup.2                                                                          20      0.4     B     100   55.2                                                                              122,000                                                                            24,700                              __________________________________________________________________________     .sup.1 Condition A: no water; Condition B: 0.24 parts water; Condition C:     0.24 parts water plus water to keep temperature under 115° C.          .sup.2 Hard phase composition: IBMA/MAA = 94.8/5.2                            .sup.3 Best for pressure sensitive adhesive.                             

EXAMPLE XX -- Sequential Polymerization -- Water Added to FirstCopolymerization.

A flask containing toluene (76.0 g.) isobutyl methacrylate (51.4 g.) andmethacrylic acid (1.96 g.) is heated to 105° C. and treated with toluene(5.0 g.) and tertbutyl peroctoate (0.85 g.). The reaction mixture isbrought to reflux (115° C.) and held there for 15 minutes. Water (4.0ml.) is added to decrease the reflux temperature to 100° C. A solutionof toluene (5.0 g.) isobutyl methacrylate (217.0 g.), methacrylic acid(8.3 g.) and tert-butyl peroctoate (3.6 g.) is then added at a uniformrate over a 45 minute period. The final temperature is 110° C. Moretoluene (10 g.) is added. The reaction mixture is maintaned at refluxfor an additional 15 minutes and then treated over a 30 minute periodwith a solution of toluene (8.6 g.) and tert-butyl peroctoate (0.48 g.).The reaction mixture is then refluxed for 15 minutes at 106° C. A softphase monomer mix prepared from toluene (87.0 g.), butyl acrylate(1067.0 g.), tert-butylaminoethyl methacrylate (48 g.) and tert-butylperacetate (0.75 g.; 75%) is fed at a constant rate over a 100 minuteperiod. During this addition, the reflux temperature increases to 130°C. Toluene (10 g.) is added. Reflux is maintained for 15 minutes andthen a catalyst solution of tert-butyl peracetate (3.0 g.; 75%) intoluene (28.6 g.) is added at a constant rate over a 60 minute period.The reaction mixture is refluxed for an additional 15 minutes and thenwater (3 ml.) and toluene (19.6 g.) are removed by azeotropicdistillation. The final solids of 86.5% indicates 100% conversion ofmonomers. The solvent is removed with a flashevaporator at 175° C. at 3to 5 torr. to a nominally 100% solids liquid with a viscosity of 16,600cps (Brookfield NBT Viscometer, Spindle 27, 20 rpm at 177° C.).

What is claimed is:
 1. A process for preparing an adhesive fromcopolymers A and B, the composition comprising:(A) from about 5 to about95 parts by weight of an addition copolymer having a Tg in the range offrom 0° to -85° C. comprising:1. from about 85 to 99.5 parts by weightof a monomer or monomers selected from alkyl (C₂ -18) or alkoxyalkylacrylate and
 2. from about 0.5 to about 15 parts by weight of anethylenically unsaturated amine, carboxylic acid, sulfonic acid, ormixtures thereof, with B. from about 5 to about 95 parts by weight of anaddition copolymer having a Tg in the range of from about 20° to 150° C.comprising:1. from about 85 to about 99.5 parts by weight of a monomeror monomers selected from a monomer of the formula: ##STR4## wherein Ris hydrogen or methyl and R¹ is lower alkyl, lower cycloalkyl orisobornyl and
 2. 2. from about 0.5 to about 15 parts by weight of anethylenically unsaturated amine, carboxylic acid or sulfonic acid ormixtures thereof, which comprises the steps of:a. polymerizing themonomers to form copolymer B by gradual addition, solutionpolymerization in an organic solvent at reflux in the presence of 0 to 5parts of water per 100 parts of the monomers used to make copolymer B b.adding to copolymer B 0 to 5 parts of water per 100 parts of monomer tobe added in step (c) and then c. adding to copolymer B the monomer mixwhich is to be polymerized to form copolymer A, d. and polymerizing themonomer mix added in step (c);at least 0.1 parts of water being presentduring the polymerization of one or both of copolymers A and B.
 2. Theprocess of claim 1 wherein water is present during the initialpolymerization of copolymer A and additional portions of water in therange of from about 0.01 to about 0.12 parts per 100 parts of totalmonomer mix per addition are added during the polymerization ofcopolymer A.
 3. The process of claim 1 in which at least 0.1 parts ofwater is utilized in the preparation of copolymer B.
 4. The process ofclaim 1 in which water in the amount of at least about 0.1 parts isutilized in preparing copolymer A.
 5. The process of claim 4 in whichcopolymer B is prepared in the absence of water.
 6. The process of claim5 in which copolymer B contains a minor proportion of a polymerizedacid-containing monomer, copolymer A contains a minor proportion of apolymerized amine-containing monomer, and copolymers A and B arecompatible.
 7. The process of claim 1 in which polymers A and B arecompatible, and the solvent is a hydrocarbon.
 8. The process of claim 2in which polymers A and B are compatible, and in which the solvent is ahydrocarbon liquid.
 9. The process of claim 3 in which polymers A and Bare compatible, and in which the solvent is a hydrocarbon liquid. 10.The process of claim 4 in which polymers A and B are compatible, and inwhich the solvent is a hydrocarbon liquid.
 11. The process of claim 5 inwhich polymers A and B are compatible, and in which the solvent is ahydrocarbon liquid.
 12. The process of claim 5 in which copolymer Bcontains a minor proportion of a polymerized acid-containing monomer.